96 S-10 Ac Issues

[Newgmer]

96 S-10 with 120k. Well maintained. No recent engine work. Vehicle AC has not worked in years.

 

I have recently acquired this vehicle and I am trying to repair the little nagging problems it has. AC is my latest challenge. Here is what I know.

 

Using the controls on the dash I know that the ventalation system works. Vacuum is changing vents and air is coming out the right vents. Heat does work correctly. AC Compressor will not engage though.

 

Thinking that the AC has a leak and no refrigerant I bought a recharge kit with a guage on it. I start the vehicle and attach the guage. System reads about 35psi. On the kit is says this is a Green area and acceptable.

 

I decide to add some refrigerant anyway. I add a little too much and get it near 45psi. The compressor kicks on and begins to cycle on and off. It goes on when the pressure reaches 45psi and then goes off when the pressure drops back to around 20psi which takes just a few seconds. Since 45psi is the 'yellow' area I let out some of the refrigerant so that the compressor stops cycling.

 

So at this point I know I have a good charge and a compressor that will engage. So I start poking around online and find a site that suggests some test you can do. I figure out that the accumulator has a sensor on it that acts as a low pressure switch. I remove the connector and short the to wires. The compressor kicks on and stays on, however the AC never gets cold.

 

So I have a compressor that somehow seems to be functioning enough to affect the pressure in the system, but I have to short the low pressure switch to get the compressor to engage. The system appears to be fully charged, but generates no cold air when forced to run.

 

Anyone out there than can make some suggestions on what else I can do to locate the problem?

 

Mark

[bobcat5544]

To start off from what you just stated. The system is low on freon. When you added freon it started to working kicking on and off which is good. You need to get the pressures on the guage up around 50-60 don't worry about the colors on the gauge. When you add freon make sure you have the truck running with the ac on. When you add freon you will notice the compressor to stay on longer. You will see on the guage that when the compressor goes off th pressure will go up around 60 psi then the compressor will kick on and go down to 20 psi then kick off. If the compressor does not kick off and stays around 30-35 psi idle the truck up and see if it kicks off. If it does then you should be good to go.

[Newgmer]

To start off from what you just stated. The system is low on freon. When you added freon it started to working kicking on and off which is good. You need to get the pressures on the guage up around 50-60 don't worry about the colors on the gauge. When you add freon make sure you have the truck running with the ac on. When you add freon you will notice the compressor to stay on longer. You will see on the guage that when the compressor goes off th pressure will go up around 60 psi then the compressor will kick on and go down to 20 psi then kick off. If the compressor does not kick off and stays around 30-35 psi idle the truck up and see if it kicks off. If it does then you should be good to go.

 

 

Ah so the pressure measurement is only valid when the compressor is engaged and running? It's ok to be much higher when the compressor is disengaged?

 

BTW thanks for your response.